The invention relates to electroslag refining systems and methods for electroslag refining. In particular, the invention related to bottom pour electroslag refining systems and methods.
Electroslag refining (ESR) comprises a process that is generally used to melt and refine various metals. For example and in no way limiting of the invention, iron (Fe), nickel (Ni), cobalt (Co), and titanium (Ti) based metals and alloys can be refined by an electroslag refining system and process. Typically, electroslag refining system comprises an consumable electrode formed from the alloy to be melted and refined, a liquid slag, and a cooled crucible, such as but not limited to a water-cooled copper crucible. The liquid slag can be heated by passing an electric current from a suitable current source to the consumable electrode then through the liquid slag and then to the crucible.
The liquid slag is maintained at a temperature that is high enough to melt the consumable electrode. A refining process occurs as the consumable electrode melts and passes through the liquid slag. Also, inclusions, such as oxide inclusions, are exposed to the liquid slag and are dissolved, thus further refining the metal. The refining process includes the melting of metal from the consumable electrode and the formation of molten metal droplets. These droplets fall, for example by gravity, through the liquid slag, and are collected in a liquid metal pool. The pool is contained by the crucible, which is generally disposed below the pool.
Electroslag refining systems generally include an induction-heated, segmented, water-cooled copper guide tube or cold induction guide (CIG). The cold induction guide is typically connected to the bottom of the electroslag refining system crucible. The cold induction guide includes an orifice from which a refined metal liquid stream can be extracted therefrom. This stream can be used as a liquid metal source for many solidification processes, including, but not limited to, powder atomization, spray deposition, investment casting, melt-spinning, strip casting, slab casting, and nucleated casting. Electroslag refining systems and cold induction guide structures are known in the art, for example as set forth in U.S. Pat. No. 5,160,532 to Benz et al., which is assigned to the Assignee of the instant invention and fully incorporated by reference.
While known electroslag refining systems are effective in refining of metals, a cold induction guide structure may be used for facilitating a flow of refined liquid metal out of the electroslag refining system. The use of a cold induction guide structure includes the addition of further current and heat to the electroslag refining system. Of course, this addition current and heat adds costs to the refining process. Also, the additional heat and current may provide insulation concerns, including heat and electrical insulation concerns.
Therefore, a need exists for an electroslag refining system that avoids adding additional heat and current to the electroslag refining system for facilitating refined liquid metal flow.
An aspect of the invention provides a bottom pour electroslag refining system. A bottom pour electroslag refining system refines raw material from a source of raw material into refined liquid metal. The bottom pour electroslag refining system comprises an electroslag refining crucible; a slag; a bottom pour structure that comprises an orifice from which refined liquid metal from the electroslag refining crucible can flow as a stream of refined liquid metal; and a current path. The current path is defined in the bottom pour electroslag refining system for applying current to the raw material for melting and refining the raw material. The melted and refined raw material forms a refined liquid metal pool in the electroslag refining crucible. The current that is applied by the current path is sufficient to provide the refined liquid metal in the refined liquid metal pool with a viscosity under which the refined liquid metal can flow through the orifice under its own viscosity.
A further aspect of the invention provides a bottom pour electroslag refining method for refining raw material from a source of raw material into refined liquid metal in which the refined liquid metal can flow under its own viscosity. The method comprises providing raw material to be refined; providing an electroslag refining crucible; providing a slag in the electroslag refining crucible; providing a bottom pour structure for the electroslag refining crucible comprising an orifice from which refined liquid metal from the electroslag refining crucible can flow as a stream of refined liquid metal; establishing a current path; applying current to the raw material from the source of raw material for melting and refining the raw material; and forming a refined liquid metal pool in the electroslag refining crucible. The step of applying current comprises applying current at an amount that is sufficient to provide the refined liquid metal in the refined liquid metal pool with a viscosity so the refined liquid metal can flow out of the orifice under its own viscosity.
Another aspect of the invention provides a bottom pour electroslag refining method for refining raw material from a source of raw material into refined liquid metal in which the refined liquid metal can flow under its own viscosity. The method comprises providing raw material to be refined; providing an electroslag refining crucible; providing a slag in the electroslag refining crucible; providing a bottom pour structure for the electroslag refining crucible comprising an orifice from which refined liquid metal from the electroslag refining crucible can flow as a stream of refined liquid metal; establishing a current path; applying current to the raw material from the source of raw material for melting and refining the raw material; and forming a refined liquid metal pool in the electroslag refining crucible. The step of applying current comprises applying current at an amount that is sufficient to provide the refined liquid metal in the refined liquid metal pool with a viscosity so the refined liquid metal can flow out of the orifice under its own viscosity. The step of applying current comprises at least one of: establishing a refined liquid metal pool that comprises a depth sufficient for the refined liquid metal to maintain a viscosity under which the refined liquid metal pool can flow through the orifice under its own viscosity; and applying current at a level that is sufficient to heat the refined liquid metal pool to a temperature in which the refined liquid metal pool maintains a viscosity under which the refined liquid metal can flow through the orifice under its own viscosity.
Another aspect of the invention sets forth a bottom pour system for electroslag refining of raw metallic material. The bottom pour system comprises means for electroslag refining; means for applying an electrical current to the means for electroslag refining; and means for producing a refined liquid metal pool. The current applied by means for applying current is sufficient to provide refined liquid metal in the refined liquid metal pool with a viscosity under which the refined liquid metal can flow through under its own viscosity.
These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention.